The present invention relates to a class of polypeptides useful in diagnostic assays to determine the presence of antibodies to Mycoplasma organisms in mammals, particularly in pigs or hogs. The invention also relates to recombinant-DNA methods for the manufacture of these polypeptides and recombinant phage clones containing DNA sequences suitable for use in the recombinant methods. The invention also relates to vaccination compositions and methods of vaccination to inhibit Mycoplasma infections in animals.
Enzootic pneumonia of pigs, also known as virus pneumonia, infectious pneumonia, anterior lobe pneumonia, enzootic virus pneumonia and mycoplasmal pneumonia of swine, rarely causes death, but often results in severe morbidity and reduced performance in weight gain of swine. Originally believed to be caused by a virus, it was determined in 1965 that the causative agent was Mycoplasma hyopneumoniae, also known as Mycoplasma suipneumoniae.
The disease is transmitted from pig to pig through the nasal passages by airborne organisms expelled from infected pigs. The Mycoplasma establish themselves deep in the apical and cardiac lobes of the lungs where they cause visible plum colored or gray lesions and cause difficulty in breathing and reduced weight gain. The primary infection by M. hyopneumoniae may be followed by secondary infection by other mycoplasma species (M. hyorhinus and M. floculare) as well as bacterial pathogens (Pasterella and Bordetella species).
The Mycoplasmas are prokaryotic cells smaller and simpler in structure than bacteria, but more complex than viruses. Unlike viruses, they are capable of a free living existence, though they are often found in association with eukaryotic cells. They are bounded by a cell membrane but not by a cell wall. They have an extremely small genome, approximately 750,000 base pairs in length.
While this disease is not often fatal, it causes decreased growth and weight gain in the affected animals at a time when the animals are being fed for market. Thus, animals which have been infected with this organism will be worth less at slaughter than will their non-infected counterparts.
Due to the serious economic consequences of pig pneumonia, diagnostic testing methods have been sought which will indicate the presence of an infection caused by Mycoplasma hyopneumoniae in swine. The present inventors have discovered a class of polypeptides useful in the diagnosis of this and certain other Mycoplasma infections. These polypeptides, when used in in vitro diagnostic assays, indicate the presence of antibodies against certain Mycoplasma organisms in infected pig and hog sera.
To facilitate use of these polypeptides, the present invention also relates to recombinant-DNA methods for manufacturing the polypeptides. These recombinant-DNA methods utilize DNA sequences contained in various recombinant phage clones which are described herein.
Another object of the present invention is to provide a vaccine composition and a method of vaccination effective for preventing certain Mycoplasma infections in animals.